Magnesium

[Ted]

Saw the Maico billet plates at the Buladelah Vinduro on the weekend. One on a 490, the other on his 250. They sure look nice.

The owner told me he just built the 490 up and took it for a squirt down the road. Got up to approx 50 kph and pulled the front brake on to turn around. The front backing plate shattered, spun around and smashed a section of the lower fork leg clean off. Scary shit.

Then he put the billet ones on. Happy days now

I can see why guys are nervous of the old magnesium plates. Safety HAS to come first and foremost.

[oldfart]

Shane .... sorry . The cats out of the bag now 

[Lozza]

Things like this are a real non issue. A) amend the rules to allow a similar or reproduction part to be used B) remove intact part have it 3D scanned scour the net looking for a company to reproduce the item. Top it off with a bit of CNC, there is even a member here that can cast reproduction items.
Not a lot of foundries want to cast magnesium, think there is only 1 in Australia.

[Nathan S]

Are the billet alloy plates heavier or lighter than the stock magnesium ones?

Lots of drum braked Yamahas used magnesium brake plates - never heard of them being a problem. And there are alloy alternatives if anyone is nervous.

So:
74 KXes can use TS185 hubs (and brake plates?);
YZ-As can use MX-A parts;
CZs have similar aluminium alloy replacements available.

The only real problem is the Maico brakes plates?!

[sa63]

there aren't many Maico  AW mag hubs in service any more - all cracked....

PES/ CCM Britain is making replica hubs + backing plates to replace the CCM  mag items, which  can fail , or are regarded as valuable.. I think the modern hubs offer better braking though ( materials +accuracy)

[JohnnyO]

Saw the Maico billet plates at the Buladelah Vinduro on the weekend. One on a 490, the other on his 250. They sure look nice.

The owner told me he just built the 490 up and took it for a squirt down the road. Got up to approx 50 kph and pulled the front brake on to turn around. The front backing plate shattered, spun around and smashed a section of the lower fork leg clean off. Scary shit.

Then he put the billet ones on. Happy days now

I can see why guys are nervous of the old magnesium plates. Safety HAS to come first and foremost.

Exactly the same thing happened to me!
I was testing my 490 Maico beside a busy road and pulled front brake on in 5th gear and backing plate mount sheared, snapped fork bottom off at axle and sent me careening onto the busy road with no steering narrowly missing several cars! Scariest thing ever!
Hence the Yamaha front wheel in my Maico and my concern over the std backing plate rule in the new proposed Evo rules.. understandable I think.

[sa63]

Also saw   brett downs front brake plate break at Harrisville on a bike I used to own (maico MC250 81) - broken ribs and a wrecked helmet a year or so ago.
Id bought the bike with a Yamaha wheel (the original owner had done the conversion in the 80s)but I changed it back...

[William Doe]

Issues of this nature will become more and more common as itime goes on i guess.
Its good to be proactive about it now and look at solutions . Saftey must be paramount followed by era sympathy . The point has already been raised that the PES  CCM hubs offer better braking performance over the originals  i cant see how this is a problem as long as they are available to anyone .
I dont like to see old bikes with lots of polished shiny billet , and would prefer if the owners would paint or coat items to a more period finish.

[William Doe]

Are the billet alloy plates heavier or lighter than the stock magnesium ones?

Lots of drum braked Yamahas used magnesium brake plates - never heard of them being a problem. And there are alloy alternatives if anyone is nervous.

So:
74 KXes can use TS185 hubs (and brake plates?);
YZ-As can use MX-A parts;
CZs have similar aluminium alloy replacements available.

The only real problem is the Maico brakes plates?!

Nath 74 KXs have a brake locking indent in the backing plate that is very wide ( like the Hondas) so alternatives (other than 75/76 KXs) are not a bolt on option  i have looked into it .

[William Doe]

Didn't Rob Tumes go down in a heap at Mt Kembla Nats when front hub fell apart on his KX ? think he went to ts185 front hub, but not sure.

Not without a fork change to Mike

[Nathan S]

OK, so the 74 KXes (hubs and brake plates?) and the Maico brake plates are the real problems?

Kawis may be able to use F11 parts, TBC.

Any others?

[HeavenVMX]

Saw the Maico billet plates at the Buladelah Vinduro on the weekend. One on a 490, the other on his 250. They sure look nice.

The owner told me he just built the 490 up and took it for a squirt down the road. Got up to approx 50 kph and pulled the front brake on to turn around. The front backing plate shattered, spun around and smashed a section of the lower fork leg clean off. Scary shit.

Then he put the billet ones on. Happy days now

I can see why guys are nervous of the old magnesium plates. Safety HAS to come first and foremost.

Exactly the same thing happened to me!
I was testing my 490 Maico beside a busy road and pulled front brake on in 5th gear and backing plate mount sheared, snapped fork bottom off at axle and sent me careening onto the busy road with no steering narrowly missing several cars! Scariest thing ever!
Hence the Yamaha front wheel in my Maico and my concern over the std backing plate rule in the new proposed Evo rules.. understandable I think.

What proposed rules?? You cannot even resist when Dave is trying to genuinely get feedback on a serious issue. Strictly speaking the current rules don't allow billet backing plates either but lets not turn this into another BUN fight.

Heaven VMX never questions the billet backing plates for Maicos because it is a safety issue they offer no real performance gain over the originals except they are trouble free and don’t try to kill anyone.

Congratulations Dave on opening a serious issue up to constructive input. Parts that allow bikes to stay on the track by replacing suspect or unobtainable parts are essential.

***This my personal input not Heaven VMX
Classic Trials bikes in the Pre65 class also have issues with wheel hubs and brake components. They have chosen a good hub from the period, in the case of Pre65 that is a Honda hub and brake available in 1964 (only just). This hub just happens to be virtually identical to the Postie bike hubs still available today. This is a very cheap and easy solution that works and is equal for everyone.

Possibly a similiar solution for our sport could be the Yamaha conical front and alloy rear hubs pretty much standard on every Yammie dirt bike from about ’71 until ’80 including trail bikes. I know this is not a purist approach but ensures a ready supply of wheels with very affordable rims and spokes, good brakes. I realise another hub would be required for right chain final drive machines but I am sure another hub could be nominated.

[GMC]

I don’t understand the dilemma
Replica parts are accepted, so are these billet backing plates really that different from stock?
They may have a slightly different outside appearance but the inside would have to be essentially the same to be able to fit and work.
How exact does a replica need to be?

The only way I can see that a billet backing plate can be a performance advantage is if they are stiffer, and if that’s the case then the original backing plate that is flexing will be prone to breaking one day. If you keep bending a piece of metal back and forth it will eventually fatigue and break.

[SON]

I have fond memories of the VB Montesa but with Magnesium Marzzochis there is no way I would ride one in anger

[supersenior 50]

My '79 Maico front backing plate failed, yet my '64 CZ is still ok (I hope). An example of why we have to be carefull with any proposed rule changes. It's so easy to cure one perceived problem and create a heap of new ones.